An update on my engine swap efforts. First, my thanks who provided comments: they did help. The oil pan swap was, as I hoped, a fairly easy change. The sump on the '34 oil pan is only about 2 inches forward of the location on the P25 pan. Internally, the baffling in the pan, and the oil pick-up screens were quite different. Fortunately, the oil pick-up location was the same on both engines is the same, and the pan went on with no problems. The hardest part was all the cleaning, and getting the gaskets properly fitted.
The starter problem took a little more research. I found that the early hemi V-8 (1951 to 1955), like the early flathead 6 cylinder engines, used a 146 tooth flywheel, and a starter with a 9 tooth pinion. They also both mount into a 3.25 inch opening in the bell housing, and the mounting bolt pattern is the same. While a couldn't find a listing for a mini, gear reduction starter for a flathead, they are available for a hemi. I bought a starter from "Promaster", and, with a little grinding on the block for clearance, it bolts into place. (I could have ground the starter mounting flange, but was reluctant to take a grinder to my new starter. I did the test fit on scrap/cracked P15 block.)
The starter is made with a series of mounting holes to allow the actual starter to be indexed relative to the mounting flange. I did have to rotate the starter one position from the location "as shipped", but that shift and the minor grinding were the only changes I needed to make. I still need to verify proper depth of engagement with the flywheel. Based on the catalog information, it should be close, but some adjustment may be needed (either shimming or grinding). The starter does require a 12 volt system, however, that change was already part of my rebuild plan so it isn't any extra effort/expense for my project.